Three things political operatives agree on: The presidential campaign pitting Al Gore against George W. Bush will be exceedingly nasty. Negative advertising may be ugly, but it's powerful. And we're about to see a lot of it.

"Normally," said Secretary of State Bill Jones of California, "I would argue that a negative campaign would dampen the ability to bring in new voters."

Dan Schnur, who served as spokesman for former Republican presidential candidate John McCain, added the equation's second part:

"You'll hear political operatives say that a negative campaign is the only thing that works," Schnur said; his skin, perhaps, still smarting from the negative attacks his own candidate sustained at the hands of the Bush forces.

This conventional political wisdom, though, may not be nearly as wise as operatives have come to think. The coming Gore-Bush smack-down could well be awfully muddy, but a unique new study suggests the consequences of negative political advertising are far more ambiguous than commonly thought.

In fact, a team of political scientists has concluded that negative advertising is no more effective than positive advertising. Moreover, the researchers concluded that negative ads don't appear to have especially detrimental consequences for voters and the political system.

"I think negative advertising is a pretty small tail, that's thought to wave a really big dog," said study co-author Lee Sigelman, a political-science professor at George Washington University.

The study published in the December issue of the American Political Science Review isn't necessarily embraced by the people who live and die by political advertising. Robert Lapsley, Jones's politically experienced undersecretary of state, shook his head incredulously when informed of the results. If negative advertising doesn't work, he questioned, then why did the negative campaign run by Republican Michael Huffington come within two percentage points of upsetting Democratic Sen. Dianne Feinstein in 1994?

"We're not saying there are no circumstances where a 'good' negative campaign wouldn't work," replied Rutgers University political science professor Richard Lau, one of Sigelman's three co-authors. Rather, Lau and Sigelman undertook a first-of-its-kind analysis of the myriad existing studies of negative political advertising.

In an academic ordeal that Sigelman said took "just short of forever" - in reality, about four years - the political scientists evaluated 52 previous studies that attempted to gauge the effects of negative political advertising. These previous studies included an oft-cited 1995 book by MIT political scientist Michael Ansolabehere and Stanford professor Shanto Iyengar called "Going Negative: How Campaign Advertising Shrinks and Polarize the Electorates."

That study found, among things, that negative ads depressed voter turnout; one explanation; some speculate, for the California voter turnout that's fallen from 60 percent of eligible voters in 1958 to 41 percent in 1998. If true, such findings matter.

"The question is not just of passing interest to casual observers of the American political scene," Lau and Sigelman wrote. "For those who believe that politics matters ... knowing whether a popular campaign tactic 'works' is important information...in the heat of a campaign, long-term qualms about the corrosive effect of negative ads on participatory democracy may well give way to the immediate goal of winning an election."

But of 30 studies dealing with the impact of negative ads on the political system, "Going Negative" notwithstanding, roughly half examined by Lau and Sigelman found no real impact. When the studies were adjusted for sampling error and other factors, Lau, Sigelman and their two co-authors concluded there was "little evidence to warrant the fears of those who believe that electoral participation is imperiled by the increasingly widespread use of negative political advertisements." Nor, they concluded, was there evidence across all the studies that negative ads are any more effective than positive ads.

Specifically, the studies show negative ads as a whole aren't any more memorable than positive ads. So why do so many people think otherwise?

"People don't like negative ads, and I expect they make a pretty good whipping boy," Sigelman said. Also, "the guys who lost need to have an explanation for why they lost."

But the new study will certainly not end the disputes either among political scientists or among political operatives. Iyengar, for one, said Friday that "I don't believe the (new study) results challenge our conclusions at all;" in part, he said, because the polls and surveys cited as part of the new study provide flawed tests of "negativity."

In the same December issue of the American Political Science Review, Iyengar and his co-author re-examined 1992 election data and concluded, again, that "exposure to negative advertising lowers intentions to votes."

Numerous other questions will likewise keep the politically inclined pondering for years. Iyengar, for instance, said an "important question" revolves around the relationship between visual and spoken information in a negative ad. He maintains a Web site devoted to such issues of political communication.

For their part, Lau and Sigelman say no one has really measured the long-term, as opposed to short and medium-term, impact on the political system of negative ads. For instance, how much does constant Washington-bashing - as distinct from the bashing of a specific opponent - undermine respect for public institutions?

Whatever their impact, however, no one doubts the negative ads will proliferate this presidential season. For instance, a new study by the University of Pennsylvania's Annenberg Public Policy Center found that at least $114 million has been spent so far by outside groups seeking to influence the 2000 presidential election - and 40 percent of the ads explicitly attacked a candidate. "The general election campaign is only a few days old, and Gore and Bush are already tearing each other's skin off," Schnur said.